BAGHDAD
— The diplomatic tussle over Iran's controversial atomic program has heated up in advance of a meeting Thursday of the UN's nuclear watchdog.

Iran's parliament passed a bill Monday that would oblige the government to "stop voluntary and nonlegally binding measures," such as intrusive snap UN weapons inspections, and to resume uranium enrichment if Iran is referred to the UN Security Council for possible sanctions.

Diplomats at the International Atomic Energy Agency (IAEA) in Vienna say there is little chance that Iran will be sent to the Council this time, despite a September IAEA resolution that found Iran in noncompliance.

But despite tough rhetoric about its right to enrich uranium for nuclear power - and Iranian resumption last week of uranium conversion, contrary to IAEA requests - Iran has taken several recent cooperative steps, including granting full access to several suspect sites that include a military high-explosives facility at Parchin.

"Everyone expects there will be some great flash of blinding light on the road to Damascus, when everything will be clear, but it is hugely complex," says a Western diplomat in Vienna. The case is "like water on rock - it does wear down, [but] it requires a lot of patience and sensitivity."

Two compromise solutions are now in play, a Moscow one backed by President Bush, and a broader one from the IAEA to create internationally monitored nuclear fuel facilities.

The Russian plan recognizes Iran's right to nuclear fuel technology, but denies it the ability to enrich uranium to levels suitable for bombs. Iran would process the uranium ore into gas, then send it to Russia for enrichment; spent fuel from the reactor would be returned to Russia.

Though Tehran has not dismissed the proposals outright, it says it should fully control its own nuclear fuel cycle. Last week, Iran took out a full-page ad in The New York Times, explaining its program and calling for a negotiated solution. Russia has significant clout, because it is building Iran's first nuclear-power plant at Bushehr. Moscow has been involved for years in negotiating terms to provide Iran with nuclear fuel, and have Iran return the spent fuel to Russia, with no chance of leakage.

The vote to suspend voluntary steps easily passed in Iran's conservative-controlled parliament, with 183 of 197 votes in favor. President Mahmoud Ahmadinejad, who recently declared that Israel should be "wiped off the map," vows that Iran will not compromise on nuclear know-how - a popular stance in the Islamic Republic.

The latest report by the IAEA Director General Mohamed ElBaradei, issued last Friday, notes that Iran had been "more forthcoming," adding however that Tehran's "full transparency is indispensable and overdue."

Perhaps more significant is the discovery - in a trove of documentation that Iran gave the IAEA - of a design experts say could only be used for a nuclear weapon. Critics say it is proof of Iran's ambition to acquire a nuclear weapon, a goal that the US and many Europeans believe Iran is determined to achieve.

Iranian officials say the diagram was unsolicited, and part of a black-market offer made by the nuclear network of Pakistani A. Q. Khan to Iran in 1987. Foreign Ministry spokesman Hamid Reza Asefi dismissed as "a sheer lie" speculation that the design proves Iran is pursuing nuclear weapons.

"Was this a teaser? We don't know," says the Western diplomat. "The fact remains, we have to check out the information."

One source familiar with the document says it is of an "old-fashioned" Chinese design, consistent with blueprints sold to Libya by the A. Q. Khan network in the 1980s. The IAEA report notes it deals with "the casting and machining of enriched, natural and depleted uranium metal into hemispherical forms."

The Western source says it is "not a core of a weapon," as has been described in some media reports, but an element used to increase the yield of a nuclear blast by slowing down the process. There are no dimensions, he says, but it would be large.

"It's obviously not innocuous - any design for a weapon is heavy stuff," says the source, who asked not to be further identified. "But in the big picture, it's not the scary suitcase bomb.... This thing wouldn't fit in a missile, not even in a truck. They would need the Enola Gay [the US plane which dropped the atomic bomb on Hiroshima in 1945], and they don't have that."

Still, many questions remain. Mr. ElBaradei's report repeats the call to suspend enrichment-related activities, and notes "no new developments with regard to questions and access" at a site at Lavisan-Shian, which was bulldozed last year, and where a layer of topsoil was removed.

Iran has signed but not ratified the Additional Protocol of the nuclear Non-Proliferation Treaty (NPT), which allows for snap inspections of any suspect site.

The IAEA report came days after details emerged in The New York Times of US briefings for ElBaradei and senior delegates last July. They were based on a computer acquired by US intelligence from a "long time" source in Iran who has since died, the Times reported, and are alleged to show missile-cone designs consistent with a nuclear payload. Saying they must protect the source, US officials have so far refused to specify the provenance of the data, or to show the original data to the IAEA.

European Union foreign-policy chief Javier Solana said the vote in Iran's parliament was "not good news." French Foreign Minister Philippe Douste-Blazy - whose nation, with Britain and Germany, was in talks with Iran until August - said "negative signals" were coming from Tehran.

But Security Council action is unlikely, as Russia and China oppose such a move. "We do not see such a threat [of Iran acquiring nuclear weapons] at the moment," Russian Foreign Minister Sergei Lavrov said Monday. "Under the current situation, while Iran is not working on enriching uranium, we should continue operating within the IAEA."